1. Field of the Invention
The present invention relates to an optical disc apparatus. More specifically, the present invention relates to an optical disc apparatus for, when an optical beam spot formed by an optical head is positioned in a bar code area, controlling the optical head so that the optical beam spot moves toward a control data area adjacent to the bar code area in a radial direction of an optical disc.
2. Description of the Related Art
An optical disc with a bar code (or a bar-coded optical disc) is known as a bar-coded read-only information recording medium (hereinafter, referred to as a “bar-coded ROM disc”). Data stored on the bar-coded optical disc is reproduceable.
A bar-coded optical disc generally includes a user data area, a control data area provided inside the user area, and a bar code area provided inside the control data area.
In the user data area, user data is recorded. User data can be, for example, music data to be reproduced by an optical disc apparatus based on an instruction of the user, or file data used in a computer. In the control data area, control data is recorded. Control data is, for example information regarding physical characteristics of a bar-coded ROM disc, such as the capacity, type and the like of the bar-coded ROM disc. In a bar code area, bar code data is recorded by means of a bar code. Bar code data is, for example, data used for preventing illegal copying of information and/or data of a production serial number of the optical disc. Unlike the user data and the control data, the bar code data is recorded in the form of a bar code. The bar code is recorded by optically processing the optical disc, for example, removing a portion of a reflective film of the optical disc or directly printing ink on the optical disc. According to one specific method for forming a bar code in the bar code area, a portion of the reflective film provided on a recording face of the optical disc is removed by a technique such as, for example, laser cutting.
Bar code data, which is recorded in a form different from that of the user data or the control data, needs to be reproduced by a device different from a device for reproducing the user data or the control data.
An example of the bar-coded ROM disc, Japanese Laid-Open Publication No. 10-97771 discloses a bar-coded optical disc including a user data area, a control data area and a bar code area.
FIG. 17 shows a structure of such a bar-coded optical disc 1700. Part (a) of FIG. 17 shows a plan view of the bar-coded optical disc 1700, and part (b) of FIG. 17 shows a cross-sectional view thereof, illustrating a positional relationship of a bar code area 1710 bearing a bar code 1750, a control data area 1720, a user data area 1730, and a ROM area 1740 of the bar-coded optical disc 1700. The bar-coded optical disc 1700 is a ROM disc, and will be referred to also as a “bar-coded ROM disc 1700”.
As shown in FIG. 17, the bar code area 1710 is provided in an inner area of the bar-coded optical disc 1700. The bar code 1750 is formed in the bar code area 1710. The control data area 1720 is provided outside the bar code area 1710, and the user data area 1730 is provided outside the control data area 1720. The ROM area 1740 includes a portion of the bar code area 1710, the control data area 1720 and the user data area 1730. The bar code area 1710 is adjacent to the control data area 1720 in a radial direction of the bar-coded optical disc 1700 and the control data area 1720 is adjacent to the user data area 1730 in the radial direction.
In part (b) of FIG. 17, R1 represents a length in the radial direction from the center of the bar-coded optical disc 1700 to the inner periphery of the bar code area 1710. R2 represents a length in the radial direction from the center of the bar-coded optical disc 1700 to the inner periphery of the ROM area 1740. R3 represents a length in the radial direction from the center of the bar-coded optical disc 1700 to the inner periphery of the control data area 1720. R4 represents a length in the radial direction from the center of the bar-coded optical disc 1700 to the inner periphery of the user data area 1730. R5 represents a length in the radial direction from the center of the bar-coded optical disc 1700 to the outer periphery of the user data area 1730. In the case where the bar-coded optical disc 1700 is a DVD, R1, R2, R3, R4 and R5 are respectively 22.3 mm, 22.6 mm, 23.5 mm, 24.0 mm and 58 mm as shown in part (b) of FIG. 17.
In the bar code area 1710, data such as, for example, an ID, a manufacturer, a lot number or a serial number of each bar-coded optical disc 1700 is recorded as the bar code 1750.
In the control data area 1720, physical format information regarding the type and format of the bar-coded optical disc 1700 (e.g., disc type, track density, or number of layers) is recorded as control data.
In the ROM area 1740, pits are formed in advance in a plurality of tracks. Data is recorded by way of the pits. Generally, no data is recorded In an area of the ROM area 1740 which is a portion of the bar code area 1710 for the following reason. The bar code 1750 is formed after the pits are formed in the ROM area 1740. Therefore, pits formed in such a portion may be undesirably defined by the formation of the bar code 1750.
In general, an optical disc apparatus includes an optical head and a control section for controlling the optical head. The optical head directs an optical beam toward a bar-coded optical disc so as to form an optical spot on the bar-coded optical disc and outputs a signal in accordance with the optical beam reflected by the bar-coded optical disc. The optical head can read information (data and address) from a portion of the bar-coded optical disc, on which the optical spot is formed, as a signal generated in accordance with the optical beam reflected by the portion.
Hereinafter, an operation of a conventional optical disc apparatus when accessing the control data area 1720 of the bar-coded optical disc 1700 will be described.
The control section controls the optical head so as to form an optical spot in the control data area 1720 of the bar-coded optical disc 1700. However, there is sometimes an error In the control of the optical head by the control section. For example, the control section cannot control the optical head so that the optical spot directly moves to the control data area 1720 because of a mechanical error in a mechanism for moving the optical head and a small size of the control data area 1720. Therefore, rather than directly positioning the optical spot to the control data area 1720, the control section first moves the optical spot outside the control data area 1720, i.e., the user data area 1730 and then moves the optical spot to the control data area 1720.
In more detail, the control section operates as follows. In the state where the optical spot is in the user data area 1730, the control section performs focusing control and then performs tracking control so as to cause the optical spot emitted by the optical head to follow the tracks of the bar-coded optical disc 1700. Thus, an address representing the position of the optical spot is read. Once the address representing the position of the optical spot is read, the control section can control the optical head so that the optical spot keeps on jumping from one track to the next track until reaching the control data area 1720. (Hereinafter, the operation of the optical spot jumping from one track to the next track will be referred to an “one-track jumping”.) In the bar-coded optical disc 1700, the user area data 1730 has information represented by pits, as in the control data area 1720. Therefore, the control section can control the optical head so that the optical spot performs one-track jumping from the user area data 1730 to the control data area 1720.
The control section cannot control the optical head to move from the bar code area 1710 to the control data area 1720. Since the bar code area 1710 has the bar code 1750, an address representing the position of the optical spot cannot be properly read from the bar code area 1710. Therefore, the control section cannot control the optical head so that the optical spot performs one-track jumping from the bar code area 1710 to the control data area 1720.
The conventional optical disc apparatus is designed only to handle a read-only bar-coded ROM disc as described above. The conventional optical disc apparatus has the following problem with a bar-coded RAM disc including a bar code area.
As described above, in general, a control section of an optical disc apparatus controls an optical head so that the optical spot repeats one-track jumping based on an address representing the position of the optical spot until reaching the prescribed address at which data is to be read.
An address representing the position of the optical spot in a bar code area of the optical disc is not accurate. Therefore, the control section cannot control the optical head so that the optical spot on the bar code area to accurately perform one-track jumping.
Accordingly, when the control section controls the optical head so that the optical head outputs a signal from a control data area adjacent to the bar code area in a radial direction of the optical disc, the control section conventionally needs to control the optical head so that the optical spot formed by the optical head does not enter at least the bar code area in order to allow the optical head to output a signal from the control data area with certainty.